Carburetor



Oct. 25, 1966 T. BARNES 3,281,132

CARBURETOR Filed Aug. 23, 1965 5 Sheets-Sheet l t N mi" go l `r Milz',Q* Q ,.\\\\m\\\\\\\. Wx

LE WELLY/V 7." BAR/VES Oct. 25, 1966` L. T. BARNES CARBURETOR Filed Aug.23, 1965 5 Sheets-Sheet 2 INVENTOR. LEM/ELL Y/V T BAR/VFS Oct. 25, 1966A T. BARNES CARBURETOR Filed Aug. 23, 1965 5 Sheets-Sheet '5 INVENTOR.ZLEWEL YA/ 7T BR/V615' United States Patent O 3,281,132 CARBURETORLlewellyn T. Barnes, 165 Meister Blvd., Freeport, Long Island, N.Y.Filed Aug. 23, 1965, Ser. No. 481,617 13 Claims. (Cl. 261-50) Thisapplication contains subject matter identical to that disclosed in myco-pending application Serial No. 127,170 tiled July 27, 1961 andconstitutes a continuationin-part thereof.

This invention relates to a carburetor for an internal combustion engineand more particularly to a down draft carburetor of a variable vacuumdesign.

The primary object of the present invention resides in the provision ofa carburetor for an internal combustion engine such as used on passengercars and the like wherein the carburetor is so designed as to permit amotor car or other automotive vehicle to operate smoothly under varyingconditions such as cornering at considerable speeds, driving at variousatmospheric conditions such as at low and high elevations, acceleratingout of a curve, and with the vehicle in a tilted position.

A further object of the present invention is to provide, in acarburetor, high jet friction for fuel so that when the throttle isclosed suddenly the fuel will not continue to iiow because of jetfriction thereby eliminating overrunning.

In accordance with an illustrative embodiment of the invention there isprovided a down draft carburetor comprising a body having an air valvemovably mounted therein. The air valve has a fuel passage therein and ametering needle is disposed in the fuel passageway for controlling theamount of fuel flow from a fuel chamber surrounding the air valve to themanifold. One of the principal features embodied in the invention ismeans for affording a variably progressive lift of the fuel needle withrespect to the lift of the air valve, so as to achieve a jet orificewhose coefficient of discharge under all ordinary conditions isapproximately constant with a ne atomizing of the fuel near the orifice.In order to achieve the variable progressive lift of the fuel needle incomparison to the lift of the air valve there is provided a linkagemeans including a cam ymounted on the air valve which is engaged by alink pivoted to the body of the carburetor, which link engages the camand the needle. An adjusting screw having another cam mounted thereon isthreadedly engaged in the body and is adapted to adjustably engage thelink on the rst cam to control the relative rate of motion of the needleand the air valve.

Another feature of the invention resides in the employment of a floatconcentric with the air valve disposed in the fuel chamber. Thisconcentric oat permits a motor car such as is used in racing to cornerat considerable speed and to accelerate out of the curve withoutstarving off the fuel supply. The concentric oat controls suitable fuelflow means for feeding fuel to the fuel chamber.

The construction of this invention -features an additional novelarrangement in parts lwherein the fuel passageway in the air valve isprovided with a venturi therein with the fuel needle extending into theventuri and being tapered upwardly so that the further the needleextends downwardly into the venturi, the greater the amount of fuel willbe able to iiow between the needle and the venturi. Because of the useof the venturi there is a tine atomizing of the fuel near the orice andmore complete combustion is achieved.

A further object of the invention resides in the provision of adown-draft carburetor which is constructed and arranged so as to permita jacket for heated water to warm the fuel air mixture to be provided.

3,Z.i,l32 Patented Get. 25, 1966 ICC The construction of the carburetoraccording to the present invention is such that the carburetor operatesunder a variable depression. When a constant suction carburetor iscalled upon to perform high duty such as in racing, it will no longerwork under its normal or designed depression. However, a higherdepression than is usually suitable for a constant suction design isalso ydesirable in order to eect atomization of the fuel when dischargerate is high. The present invention is designed to provide fineatomization of the fuel under special conditions and is designed to workat a depression as high as 25 of water at its maximum limit while thelow limit of working before `the air valve lift is 7" to 8 of water. Bykeeping the lower limit of working pressure low, the weight of themoving part, that is the air valve, and hence its inertia can be keptdown. The air valve is counterbalanced as it is inverted and balanced by-metered springs. Further, under slow running and like conditions thedepression in the mixing chamber is 4 of Water, but owing to the greatrestriction caused by the venturi tube about the orifice, the airvelocity at this point is extremely high and in the order of 200 persecond.

A further object of the present invention is to provide a carburetorwhich has means for adjustment of the spring action on the fuel needlewith respect to the air valve so that the carburetor can be adjusted foruse at both low and high altitudes.

Still further objects and features of this invention reside in theprovision of a down-draft carburetor that is simple in construction,eiicient in operation, capable of being utilized in conjunction withvarious existing internal combustion engines, and which is eflicient inuse.

These, together with the various ancillary objects and features of theinvention which will become apparent as the following descriptionproceeds, are attained by this down-draft carburetor, a preferredembodiment of which has been illustrated in the accompanying drawings,by way of example only, wherein:

FIG. l is a vertical sectional view of a down-draft carburetorconstructed in accordance with the concepts of the present invention;

FIG. 2 is -another vertical sectional view of the carburetor, taken on aplane normal to the plane of FIG. l, and illustrating in particular thecoaction between the float and the means for feeding fuel into the fuelchamber;

FIG. 3 is a horizont-al sectional view taken along the plane of line 3-3in FIG. 2 illustrating particularly the construction of the air valveand relative arrangement of the needle valve and fuel passageway in theair valve communicating with the fuel chamber;

FIG. 4 is a horizontal sectional view taken along the plane of line 4 4in FIG. 2, illustrating details of the float and fuel feedingmechanisms;

FIG. 5 is a horizontal sectional view taken along the 4plane of line5--5 in FIG. 2 and showing the air valve in a bottom plan view;

FIG. 6 is a partial elevationa-l view showing the control assembly forthe fuel metering needle at a setting for a lean fuel mixture, with theengine in starting or idling condition;

FIG. 7 is a partial elevation view similar to FIG. 6 with the assemblyset for a lean fuel mixture, but with the engine in acceleratedcondition;

FIGS. 8 and 9 are partial elevational views, similar to FIGS. 6 and 7,but showing the con-trol assembly for the fuel metering needle at asetting for medium fuel mixture, with the engine respectively atstarting and accelerated conditions; and

FIGS. l0 and ll are partial elevation view-s similar to FIGS. `8 and 9,but showing the control assembly for the fuel metering needle at asetting for rich mixture.

With continuing reference =to the accompanying drawings wherein likereference numerals designate Similar parts throughout the various views,reference numeral generally designates a down-draft carburetorconstructed in accordance with the present invention. The carburetor isprovided with a body 12 formed of several sections including a basesection 14, a central section 1o, and a -cover section 18. The base-section is designed to be connected to the intake manifold by mea-ns ofsuitable fasteners and includes a bowl 20 for receiving an atomizedfuel-air mixture for feeding past a butterfly valve 22 into themanifold. Surrounding the bowl is a jacket 24 adapted to be -illed withhot water for heating the fuel air mixture so that better vaporizationcan be obtained and so as to aid in the starting operation of theinternal combustion engine when it is cold.

The middle -section 16 of xthe carburetor is provided with ta liange 26and bolts 28 or other suitable fasteners extend through the fiange 26into the -ba-se 14 for attaching the middle section 16 of the carburetorin a detachable manner to the base. The cover 18 is likewise providedwith a `flange 30 and bolts 32 or other suitable fasteners arethreadedly engaged in the middle section 16 of the carburetor fordetachably 4securing the cover thereto.

It is to be noted that each of the sections of the body 12 a-repreferably cast from bronze or aluminum. The centra-i section 16 of thebody is provided with an inner wall 34 defining a fuel chamber 38 inconjunction with the outer wall 36 of the middle section 1-6. The fuelchamber 38 is closed off at the top by a downwardly extending projection40 of the cover 18 and by a ring 42 and a `housing 4d. The housing 44 isprovided with a iiange 46 which extends between the projection 40 and aring 42.

Also provided on the central section 16 is a fuel inlet member 48 whichhas an internally threaded portion S0 for reception of a cap 52. A fuelsupply line 54 is connected to the full inlet member 48 and is designedto feed fuel upward through the fuel inlet member and into the fuelchamber 38. ln order -to cont-rol ow of fluid there is provided a needlevalve 56 having a rod 58 attached thereto and having a pair of colla-rs60 and 62 on the rod. The collars are Iadapted to be engaged by afollower 64 which, as can be best seen in FIG. 4 is in the form of abifurcated end portion of a float bracket 66 pivoted as at 68 to thecentral section 16. The bracket 6'6 is in the form of a yoke ofsemi-circular shape and has stub axles 70 and 72 -on the ends thereofwhich stub axles engage the bearing blocks 74 and 76 fixed to a fioat 78which is Isubstantially of a doughnut or torus shape and isconcentrically disposed about the cylindrical inner wall 34 of thecentral portion 16.

The cap contains a plate 80 provided with an aperture 82 therethrough,through which the upper end 84 of the pin 58 extends. The pin 58 isprovided with a threaded portion 86 and threadedly engaged on thethreaded portion is a washer 88. A spring 90 is positioned so as to biasthe plate 80 4and the washer 88 whereby the needle valve `56 is normallyurged lto a closed position and is held out of the closed position byaction `of the yoke 66. As can lbe readily seen, `the float is in alowered position due to Ia low Ilevel of fiuid in the fuel ychamber 36.Further, when the level of fuel in the fuel chamber 38 achieves that towhich the assembly is set for optimum performance of the carburetor, byadjustment of the position of Athe threaded washer 88, the pin S8 willbe pushed downwardly until the needle 56 cuts off the flow of fluid tothe fuel chamber 38. As fuel leaves the fuel chamber 38, the needlevalve 56 will open permitting the fiuid chamber 38 to be always filledto the proper level.

The center section 16 of the body 12 is provided with a portion 100 ofreduced cross sectional dimension which has a plurality of apertures 102therethrough communicaring with -the atmosphere. Further, the angeportion 26 of the central section 16 is provided with a valve seat 104in the form of a bevelled surface which is adapted to cooperate with thebevelled surface 106 of an air valve member 108 which is slidablymovably closely iitted with the inner cylindrical wall 34 of the centersection 12. The air valve 108 has its lower portion provided with aplurality of diverging passages or -outlets 110 which communicate withthe mixing chamber 20. The bottom end 112 of the air valve member 108 isconcave. The air valve member is provided with a fuel vapor passage 114therein which communicates with the outlet 110. Further, the air valveis provided with an enlarged area 118 and a cylindrical wall 120 whichclosely engages the inner surface 122 of the cover portion 18. A coilspring 124 engages the flange 46 of the housing 44 and the shoulder 126formed by the enlargement 118, so that the spring 124 normally urges theair valve 1018 into a closed position preventing tflow of air fromentering the mixing cham-ber 20. However, when -the air valve membermoves downwardly due to suction induced in the mixing chamber 20 andapplied against the bottom surface of the air valve member, the airvalve member will be sucked downwardly against the action lof the spring124 permitting fiow of air into the mixing chamber 20 and thence intothe manifold.

A metering needle 130 is slidably, movably disposed and extends upwardlyand out of the air valve member through a -bore 132 in the upperportions of the air valve member. The metering needle 130 is providedwith a bushing or fitting 134 having a collar 136 at the upper endthereof 4and is provided with an upwardly tapering portion 138 whichcontrols ow of fluid through an orifice 140. The orifice 140 is formedin an orifice block 150 (FIG. 2) which is fixedly held in place in.association with the housing 44 and which has a tortuous passageway 152therein communicating at one end with the tube 154, which extends intothe fuel chamber 38, and at the other end with the orifice 140. Theorifice block extends through a slot in the valve lmember 108, therebypermitting downward sliding movement of said valve member relative tothe orifice block 150, which is always stationary.

Fixed in place `and held thereto by the lower portion 111 of the airvalve 108, which is threadedly detachably secured to the upper member119 of the air valve member 108, is a venturi 160. The venturi isadapted to move with the air valve 108 and the orifice yblock 150extends almost all the way through to the constriction when the airvalve is in a closed position such as during idling operation of theengine.

It will be observed that the orifice block 150, having the fuel orifice140, is a fixed portion of housing 44 and is, therefore, stationary atall times. The metering needle 130, -on the other hand, is mounted on-and carried by the 'air valve 108 such that when the air valve 108 isdrawn downwardly, the needle 130 is drawn with it, so that its narrowerupper tapered portion 138 moves into registry with the orifice 140 andpermits fuel to feed therethrough. If the metering valve 130 wererigidly secured to the air Avalve 108, the amount of fuel fed throughorifice 140 would be dependent solely on the degree of travel of saidair valve. In accordance with the invention herein, however, there isprovided an Iarrangement whereby the metering needle 130 can move at 'acontrolled rate relative to the movement of the air valve 108; that isto say, the rate of movement of needle 130 can be adjusted so that itsmovement is selectively faster than the rate of 'movement' of the airvalve 108.

In order to accomplish the aforementioned adjustment, an assemblygenerally indicated at is provided. This assembly includes a plate 172mounted on the air valve to which a multiplying lever 174 is pivoted at176. The multiplying lever 174 has a cam surface 178 which is adapted tobe engaged by a roller cam follower 18,0

rotatably mounted by means of axle 182 and the bifurcated ends 184 of alink 186 pivotally mounted at 188 on the cover section 18 of the bodyand normally urged by torsion springs 190 upwardly clockwise as shown inFIG. 1. The link 186 is provided with a notch 194 therein. A furtherlink 196 is pivoted as at 198 to the plate 172 and also pivoted -at 200to a link 202 which is pivoted at 204 to a link 206 also pivoted to theplate 172 by pivot shaft 176 making a parallelogram linkage. The link206 is thus mounted to turn in unison with multiplying lever 174. Thelink 196 is formed as a lever h-aving an angul'arly disposed integralarm 210 having a terminal cam surface which engages the collar 136 atthe upper end of the metering needle 130 yso that as the link 196rotates, it 4will translate such rotational motion to reciprocal motionof the -metering needle 130.

Threadedly secured in the cover 18 is an -adjusting cap 220 which has arecess 222 therein. Within the recess 222 there is provided a spring 224which eng-ages the cap 220 and the collar 136 on the metering needle130.

The spring 224 exerts a downward biasing force on collar 136, which inturn biases the lever arm 210 of link 196 in a downward or clockwisedirection, and urges the multiplying lever 174 in an upward or clockwisedirection through the parallelogram linkage 172, 196, 202, 206. The -camsurface 178 of multiplying lever 174 is thus biased into engagement withthe roller 180 on link 186. The lower end `of the cap 220 is shaped toextend at an oblique angle to form Ia cam 226 which engages within thenotch 194 in the link 186 to vary the inclination `of said link 186 andselectively position the roller 180 along the cam surface 178.

It will be observed in FIGS. 6-l1 that the multiplying lever 174 has amain body portion 175 having the arcuate Cam surface 178, and a terminalbody portion 177 having 4a planar cam 'surface 179 larranged at asubstantial angle to the arcuate cam surface 178.

In the position shown in FIGS. l and 6, the cap 220 is adjusted so thatthe highest point on its cam surface 226 engages the notch 194 in link186. This positions the link 186 at an angle of approximately 45 fromthe vertical, as shown in FIG. 1, and represents a setting for lean fuelfeed.

The cap 220 may be turned to the position shown in FIG. 8, representinga medium fuel feed. When this occurs, a lower portion of cam surface 226moves into engagement with notch 194, causing the link 186 to turn in acounter-clockwise direction toward the vertical. This movement permitsthe multiplying lever 174 to turn in an upward or counter-clockwisedirection, in turn, permitting the metering needle 130 to movedownwardly under the biasing force of spring 224. If the cap 220 isturned to the position of FIG. l0, in which the lowermost portion of camsurface 226 engages notch 194, the link 186 is turned to thesubstantially vertical position shown, and the multiplying lever 174moves counterclockwise to the position shown, allowing the meteringneedle 130 to move further downwardly under the force of spring 224. Theposition of FIG. 10 represents a setting for rich fuel feed.

As can be readily seen, when the metering needle 130 is in a loweredposition, the lower the position, the more iiid can flow past thetapered portion 138 of the metering needle. This tapered portion 138 hastapering and inverted slots for the purpose of metering the ow of thefluid with a high jet friction to prevent over-running of the jet upondecreasing engine speed. In other words, spillover is prevented. Thegrooves in this needle are V-cut and have rounded corners.

In the adjusted position of FIGS. l and 6, representing the setting fora lean mixture, the link 186 is disposed at such an angle that itmaintains the multiplying lever 174 at the angle shown, with theterminal body portion 177 vertically upstanding. The roller 180 islocated at the lower end of the planar cam surface 179 of the terminalbody portion, and the parallelogram linkage is so disposed that thetapering end portion 138 of metering needle 130 blocks the orifice 140.

When suction in the bowl 20 causes the valve member 108 to slidedownwardly, the plate 172, parallelogram linkage 196, 202 and 206, andmetering needle are carried `downwardly with said valve member 108. Thelink 186, however, remains stationary and its end roller 180 rides alongthe vertically-disposed planar cam surface 179 .of multiplying lever174, so that there is no pivoting movement of said lever 174, nomovement of the parallelogram linkage, and no vertical movement of themetering needle 130 relative to the valve member 108. As shown in FIG.7, the tapering portion 138 of metering needle 130 moves downwardlythrough the orifice 140 of the fixed iorice block so that a portion oflesser diameter is brought into registry with said lorifice to providean annular fuel outlet opening. It will be understood, however, that inthis lean adjustment of FIGS. 6 and 7, the metering needle 130 iscarried downwardly with the air valve member 108 at the same rate oftravel as the latter.

When the carburetor assembly is adjusted for a medium fuel mixture, asshown in FIG. 8, by turning the cap 220, as previously described, thelink 186 is pivoted downwardly, :or in a Conner-clockwise direction bythe cam surface 226 lof said ca As link 186 turns from the adjustedposition of FIG. 6 to the adjusted position of FIG. 8, the roller ridesdownwardly along the arcuate cam surface 178 of multiplying lever 174.This arcuate cam surface 178 describes an arc whose center is at theaxis of pivot 188, so that this adjusting movement does not affect theangular disposition lof the multiplying lever 174, and the meteringneedle 130 is maintained in the position in which its tapering endportion 138 blocks the orifice 140.

With the assembly set in this position of m-edium fuel feed, when thevalve member 108 is drawn downwardly by suction, the multiplying lever174 tends to move away from the roller 180. However, the spring 224,exerting a downward biasing force `on metering needle 130, thereby urgesthe arm 210 of lever 196 downwardly, causing the parallelogram linkageto shift in a direction to move the multiplying lever 174 in a clockwisedirection. The multiplying lever is thus biased to remain in engagementwith the roller 180, and as the valve member 108 moves downwardly, themultiplying lever 174 turns in a clockwise direction, lowering the leverarm l210 and permitting the metering needle 130 to be urged downwardlyby spring 224. Thus, the metering needle moves downwardiy at'a fasterrate than the valve member A108, and the tapering end portion 138extends a further distance through orifice 140, presenting an annularopening of greater diameter, as can be seen b a com a' FIG.9with FIG. 7.y p uson of When the carburetor assembly is adjusted for a rich fuelmixture, as shown in FIG. l0, the cap 220 is turned until the lowestpoint of its cam surface 226 engages the notch 194, and the link 186 isthus disposed in a substantially vertical position. The multiplyinglever 174 is biased further in a clockwise direction so that it is lmorevertically upstanding from the pivot 176, and the lower portion of itsarcuate cam surface 178 is in en a em ent with roller 180. g g

At this setting,

when suction in the bowl 20 causes the valve member 10 the orifice 140,and its small diameter provides a large annular fuel outlet opening.

The venturi 160 terminates short of the outlets 110 and the venturi willchange the rate of flow of the fuel to increase it to the extent that itflows at the rate of about 200 feet per second causing the fuel toatomize into a fine mist which is combined with air in the bowl 2) afterthe fuel has left the ,outlet 110. The air brought into the bowl 20 mayof course be filtered by a filter or screen positioned concentricallyabout the portion 100 of reduced cross sectional area by means of thecomplementary notches 260 and 262 formed in the center section 16 of theunder surfaces :of the center section 16 of the body.

The oat 78 which is concentri-cally disposed about the air valve member108 and about the fuel passage controls the operation of the fuel needlevalve 56 whereby liow of fuel into the fuel chamber 38 is controlled. Asthe speed of the engine increases, a greater suction op the bowl 20 willbe present and the air valve member 108 which is normally held inaraised position against gravity by the spring 124 will be suckeddownwardly. Dependent on the position of the link 186, the meteringneedle 139 will move with respect to the air valve member. The fartherthe metering needle 130 is permitted to move downwardly, the greater theflow of fuel into the bowl 2t) there will be.

A latitude of modification, change and substitution is intended in theforegoing disclosure and in some instances some features `of theinvention will be employed Without a corresponding use of otherfeatures. Accordingly, it is appropriate that the appended claims beconstrued broadly and in a manner consistent with the spirit and scopeof the invention herein.

I claim:

1. A carburetor comprising a body, an air valve movably disposed in saidbody, said air valve having a fuel passage therethrough, a meteringneedle disposed in said passage, first means mounting said air valve formovement in said body and second means connecting said needle to saidair valve for movement with said air valve and for relative movementwith respect thereto, adjusting means coacting with said second meansfor adjusting the relative movement of said needle with respect to saidair valve in response to movement of said air valve between one extremewhere said needle is carried by said air valve without movement relativethereto, and another extreme where said needle is carried by said airvalve and has maximum movement relative thereto, said body including achamber concentric with said air valve, said passage communicating withsaid chamber, a float concentric with said air valve disposed in saidchamber, and fuel ow means connected to and controlled by said float forfeeding fuel to said chamber.

2. A carburetor comprising a body, an air valve movably disposed in saidbody, said air valve having a fuel passage therethrough, a meteringneedle disposed in said passage, a stationary fuel orifice in saidpassage surrounding and controlled by said needle, means for adjustingsaid needle relative to said air valve to adjust the mixture of air andfuel, first means mounting said air valve in said body and second meansmounting said needle in said body for adjusting the relative movement ofsaid needle with respect to said air valve upon movement of said airValve, said fuel passage having a venturi therein surrounding saidorifice, said venturi being carried by said air valve for movementtherewith, said needle extending beyond said orifice into said venturi,said needle being tapered upwardly so that the further said needleextends downwardly into said venturi, the greater the amount of fuelthat can be discharged from said venturi.

3. A carburetor Comprising a body, an air valve movably disposed in saidbody, said body including a valve seat, spring means supporting said airvalve and urging said air valve against said seat, said air valve havinga fuel passageway therethrough, a metering needle disposed in saidpassage, linkage and cam means mounting said needle and said air valvein said body for progressively moving said needle in response tomovement of said air valve, and said linkage and cam means includingmeans adjusting said needle and air valve between one extreme where saidneedle is moved with said air valve without movement relative theretoand another extreme where said needle is moved with and has maXimummovement relative to said air valve.

4. A carburetor according to claim 3, in which said linkage and cammeans includes a first cam mounted on said air valve, means operativelycoupling said first cam with said needle, a link mounted on said bodyengaging said first cam, a second cam and means adjustably mountingsaaid second cam on said body for engagement with said link to adjustthe position of said link on said first cam.

5. A carburetor comprising a body having an air valve movably mountedtherein, spring means connecting said air valve to said body andnormally urging said air valve to a closed position during idlingoperation, means for urging said air valve to an open position by avacuum condition in said body during operation at speeds higher thanidling, said body having a fuel chamber therein, said air valve having afuel passageway therein communieating with said fuel chamber, a meteringneedle disposed in the fuel passageway for controlling the amount offuel ow from said chamber through said fuel passageway, linkage meansconnected to said air valve to engage said needle for adjusting therelative travel of said needle with respect to said air valve when saidair valve moves in response to a vacuum condition in said body, andmeans for adjusting said linkage means between a first position in4which said needle is moved with said air valve without movementrelative thereto and a second position in which said needle is movedwith and has a maximum movement relative to said air valve.

6. A carburetor according to claim 5, in which said carburetor is adowndraft carburetor and includes, a float concentric with said airvalve disposed in said chamber, and fuel flow means on said bodyconnected to and controlled by said float for feeding fuel to saidchamber.

7. A carburetor according to claim 5, in which said carburetor is adowndraft carburetor and said linkage means includes a first cam mountedon said air valve and controlling the movement of said linkage, and saidadjusting means includes a link mounted on said body for engaging saidfirst cam, and a second cam adjustably mounted on said body engagingsaid link to adjust the position of said link on said rst cam to adjustthe relative movement of said needle and said air valve.

S. A carburetor according to claim 5, in which said carburetor being adowndraft carburetor and, said fuel passageway has ra venturi therein,said needle extending into said venturi, said needle being taperedupwardly so that the further said needle extends downwardly into saidventuri, the greater the amount of fuel that can be discharged from saidventuri so that the rate of fuel flow increases at substantially thesame ratio as the rate of air flow increases.

9. A carburetor according to claim S, in which said linkage meansincludes a rst cam mounted on said air valve, a link mounted on saidbody for engaging said first cam and means operatively coupling saidfirst cam with said needle, and in which said adjusting means includes asecond cam adjustably mounted on said body engaging said link foradjusting the position of said link on said first cam to adjust therelative movement of said needle and said air valve, said carburetoralso including a float concentric with said air valve disposed in saidchamber, and fuel fio-w means on said body connected to and controlledby said oat for feeding fuel to said chamber.

10. A downdraft carburetor comprising a body having an air valve movablymounted therein, spring means mounting said air valve in said body andnormally urging said air valve t a closed position during idlingoperation, means urging said air valve to an open position by a vacuumcondition in said body during operation at speeds higher than idling,said body having a fuel chamber therein, said air valve having a fuelpassageway therein communicating with said fuel chamber, a meteringneedle disposed in said fuel passageway for controlling the amount offuel flow from said chamber through said fuel passageway, said fuelpassageway having a venturi therein, said needle extending into saidventuri, said needle being tapered upwardly so that the further saidneedle extends downwardly into said venturi, the greater the amount offuel that can be discharged from said venturi, linkage means connectedto said air valve and said needle for adjusting the relative travel ofsaid needle with respect to said air valve when said air valve moves inresponse to a vacuum condition in said body, said linkage meansincluding a rst cam mounted above said air valve, means operativelycoupling said rst cam with said needle to vary the position of Saidneedle relative to said air valve in response to movement of said firstcam a link pivoted to said body and having a roller cam followerengaging said cam, a second cam, and means adjustably mounting saidsecond cam on said body with said second cam engaging said link foradjusting the position of said roller cam follower on said iirst cam toadjust the relative travel of said needle and said air valve to controlthe richness of the air fuel mixture.

11. A downdraft carburetor according to claim which also includes a oatconcentric with said air valve disposed in said chamber, and fuel owmeans on said body connected to and controlled by said iloat for feedingfuel to said chamber.

12. A carburetor comprising a body, an air valve movably disposed insaid body, said air valve having a fuel passage therethrough, a meteringneedle disposed in said passage, iirst means mounting said air valve insaid body and second means mounting said metering needle in said bodyfor progressively moving said needle relative to said air valve inresponse to movement of said air valve such that the rate of fuel flowincreases and decreases at substantially the same ratio as the rate ofair flow increases and decreases, said second means including meansmounting said metering needle for adjustable movement with respect tosaid air valve between a first position in which said needle moves withsaid air valve and without movement relative to said air valve and asecond position in which said needle moves with said air valve and has amaximum movement with respect to said air valve.

13. A carburetor comprising a body having a stationary fuel outletorice, an air valve movably mounted in said body, said air valve havinga fuel passage therethrough, a metering needle carried by said air valvefor movement therewith relative to said stationary fuel outlet orifice,means mounting said metering needle movably relative to said air valve,a linkage mounted on said air valve and engaging said metering needlefor adjusting the position of said needle relative to said air valve, acam member connected to said linkage for varying the position thereof,and manually adjustable means mounted on said body and engaging said camfor progressively adjusting the relative movement of said needle withrespect to said air valve in response to movement of said air valvebetween one extreme in which said needle is moved with said air valvewithout movement relative to said air valve and another extreme in whichsaid needle moves with said air valve and has a maximum movement to saidair valve.

References Cited by the Examiner UNITED STATES PATENTS 1,010,185 11/1911Schultz. 1,356,661 10/ 1920 Schultz. 1,737,184 11/ 1929 Bright.2,868,522 1/1959 ONeil. 2,999,674 9/ 1961 McClain 261-50 FOREIGN PATENTS435,768 9/ 1935 Great Britain.

HARRY B. THORNTON, Primary Examiner.

RONALD R. WEAVER, Examiner.

12. A CARBURETOR COMPRISING A BODY, AN AIR VALVE MOVABLY DISPOSED INSAID BODY, SAID AIR VALVE HAVING A FUEL PASSAGE THERETHROUGH, A METERINGNEEDLE DISPOSED IN SAID PASSAGE, FIRST MEANS MOUNTING SAID AIR VALVE INSAID BODY AND SECOND MEANS MOUNTING SAID METERING NEEDLE IN SAID BODYFOR PROGRESSIVELY MOVING SAID NEEDLE RELATIVE TO SAID AIR VALVE INRESPONSE TO MOVEMENT OF SAID AIR VALVE SUCH THAT THE RATE OF FUEL FLOWINCREASES AND DECREASES AT SUBSTANTIALLY THE SAME RATIO AS THE RATE OFAIR FLOW INCREASES AND DECREASES, SAID SECOND MEANS INCLUDING MEANSMOUNTING SAID METERING NEEDLE FOR ADJUSTABLE MOVEMENT WITH RESPECT TOSAID AIR VALVE BETWEEN A FIRST POSITION IN WHICH SAID NEEDLE MOVES WITHSAID AIR VALVE AND WITHOUT MOVEMENT RELATIVE TO SAID AIR VALVE AND ASECOND POSITION IN WHICH SAID NEEDLE MOVES WITH SAID AIR VALVE AND HAS AMAXIMUM MOVEMENT WITH RESPECT TO SAID AIR VALVE.